1. Field of the Invention
The present invention relates to an operator presence sensing apparatus for a seat of a vehicle, the apparatus being operable for generating a signal when the driver (operator) takes or leaves the seat.
2. Description of the Related Art
With an operator presence sensing apparatus for a seat of a vehicle known from Japanese Patent Unexamined Publication No. 8-99559, the seat is pivotable about a pivot axis extending transversely thereof and provided in a base member supporting the seat. Also, this conventional apparatus comprises a relay member extending vertically between the base member and the seat, and a seat lift-up spring disposed between the base member and an underside of the seat for receiving part of the weight of the seat. The relay member is pivotably supported at one end thereof by the pivot axis and at the other end by the base member through a cushion spring. The seat, when unoccupied by the operator, is pivoted by the lift-up spring to a floating position above the relay member. An operator presence sensing switch is provided in the relay member for detecting that the seat occupied by the operator has pivoted from the floating position to a lowered seated position. The cushion spring, seat lift-up spring and operator presence sensing switch are aligned longitudinally of the vehicle. The operator presence sensing switch detects presence or absence of the operator on the driver's seat. Unless presence of the operator is detected, an engine is not started, or is stopped if it is running.
However, with such a conventional operator presence sensing apparatus, a pivoting range of the relay member is not taken into consideration. As a result, the relay member (hence the seat) could pivot to a great extent upward, when the seat is unoccupied, to interfere with the seat and components arranged around the relay member, thereby to cause various inconveniences.